Hand-held processing devices such as PDAs and mobile telephones have recently been configured to incorporate or support a digital camera. For example, PDAs such as the Palm Pilot™ and Handspring Visor™ are now configured to support attachable digital camera modules, as described in Cyberscope, “Gadgets From the Desert,” Newsweek, Feb. 21, 2000, page 9. An example of a mobile telephone which incorporates a digital camera is the VisualPhone VP-210 from Kyocera, http://www.kyocera.co.jp. These and other hand-held devices which incorporate or support digital cameras can be used in a variety of image processing applications, including applications such as taking still pictures or video, and video telephone services (“visiophony”).
A significant problem which can arise in the above-noted conventional hand-held devices is the lack of stability of the image content as the user manipulates the device. For example, in visiophony or other applications involving a video signal generated by a camera, it is generally desirable to have the camera automatically frame and track the user or another object of interest. This framing and tracking process not only provides a more useful video signal in terms of its information content, but also facilitates compression of the video for subsequent transmission. Unfortunately, the conventional hand-held devices described previously fail to provide effective framing and tracking features for their associated digital cameras. A need therefore exists for techniques for providing such features in hand-held processing devices which incorporate or support a digital camera.